JPH06141325A - Satellite broadcast receiver - Google Patents

Abstract

PURPOSE:To provide the satellite broadcast receiver in which a polarized wave plane of a polarizer provided to an antenna converter is always stably adjusted automatically even in any input electric field strength. CONSTITUTION:A C/N detection circuit 10 outputs a detection signal in response to the C/N of a received radio wave when a CS radio wave received by a CS converter 13 is a normal electric field and outputs a detection signal of a preset value in a weak electric field where an AGC circuit 2 is not normally operated. An antenna control circuit 11 outputs a control signal in response to the detection signal to control the polarized plane of the polarizer in the CS converter 13 so as to maximize the C/N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcasting receiver capable of automatically and stably adjusting the polarization plane of a polarizer provided in an antenna converter in any input electric field.

[0002]

2. Description of the Related Art In recent years, pay broadcasting and MUSE are used in satellite broadcasting.
With the emergence of new systems such as broadcasting, the number of broadcasting channels is increasing, and multi-channelization is progressing along with terrestrial broadcasting. Along with this, a multi-channel satellite broadcast (CS broadcast) using a communication satellite (CS) has recently appeared.

FIG. 3 shows an example of frequency arrangement in CS broadcasting. Unlike circularly polarized waves used for BS broadcasting (satellite broadcasting by broadcasting satellites), CS broadcasting waves send many broadcasting waves within a narrow frequency band, so horizontal and vertical polarization alternate for each channel. It is used for, and it is transmitted so that adjacent channels cover it in terms of frequency. Therefore, in the outdoor unit (that is, the CS converter), C
By supplying an electric signal for polarization plane adjustment from the S tuner, the polarization plane can be selected by the polarization plane selection unit (polarizer) of the CS converter.

Two examples of conventional CS broadcast receivers (CS tuners) are shown in FIG. First, the conventional example shown in FIG. 4 (A) will be described. 12G received by parabolic antenna
CS broadcasting radio wave in the Hz band is 1 GHz by the CS converter (13).
The frequency is converted to a z-band CS-IF signal (at this time, as described above, by the polarization plane adjustment signal from the CS tuner,
Polarizer of CS converter selects the plane of polarization), CS-CS of the indoor unit CS tuner by the coaxial cable
It is transmitted to the IF signal input terminal.

The CS-IF signal supplied to the input terminal is
Frequency conversion circuit via a capacitor that passes high frequency components
It is supplied to (1) and converted to an intermediate frequency band signal.
The output of the frequency conversion circuit (1) is supplied to the AGC circuit (2). The AGC circuit (2) detects the amplitude of the input signal, generates a DC AGC voltage corresponding to the detected amplitude, and controls the gain by the DC AGC voltage so that the amplitude of the output signal becomes constant.

The output signal of the AGC circuit (2) is supplied to the FM demodulation circuit (3) and is FM demodulated into a baseband signal, which is further frequency separated into a video signal and an audio signal. After the video signal is de-emphasised by the video signal processing circuit (4) and the energy diffusion signal is removed,
It is supplied to the eo output terminal. Further, the audio signal is subjected to 4-phase DPSK demodulation and PCM demodulation processing in the audio signal processing circuit (5), de-emphasised and supplied to the audio output terminal.

On the other hand, the polarization plane adjustment of the converter described above is performed by the user operating the polarization plane adjustment button provided on the CS tuner. The signal from the polarization plane adjustment button is converted into an antenna control signal by the antenna control circuit (11), and C is sent via the antenna control output terminal (12).
It is supplied to the S converter (13).

Recently, in order to automatically control the polarization plane adjustment as in the CS tuner shown in FIG.
A device using an AGC voltage generated by the GC circuit (2) has also been proposed.

However, the above-mentioned conventional polarization plane adjustment has the following problems.

In the method of adjusting the polarization plane by the polarization plane adjustment button, the polarization plane is manually adjusted by the polarization plane adjustment button while the user monitors the video signal and the audio signal output from the CS tuner. There must be. Therefore, the adjustment takes time and, at the same time, the adjustment is based on the subjective evaluation of the person, and thus the adjustment value may vary.

Further, in the method of automatically adjusting by using the AGC voltage, the AGC voltage greatly depends on the noise amount when there is no signal, so that the AGC voltage may not accurately represent the presence or absence of the received signal. Yes, the automatic adjustment was sometimes unstable. Furthermore, in this method, the AGC voltage can be used only in the input electric field range above a certain level where the AGC voltage normally operates, and the automatic adjustment rarely works.

[0012]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to adjust the polarization plane of a polarizer provided in a converter always stably and automatically in any input electric field. To make a satellite receiver that can
The point is what kind of measures should be taken.

[0013]

In order to solve the above problems, the present invention provides

A signal received by a satellite broadcasting antenna is supplied to a converter, a plane of polarization is selected by a polarizer in the converter, and then frequency conversion is performed in the converter to output a CS-IF signal. In the satellite receiver that is

A frequency conversion circuit for converting the CS-IF signal into an intermediate frequency band;

The amplitude of the output signal of the frequency conversion circuit is detected, an AGC voltage corresponding to the amplitude is generated, and the A
AGC that controls the gain by the GC voltage and keeps the output constant
Circuit,

The output signal of the AGC circuit is FM demodulated,
An FM demodulation circuit for converting video and audio baseband signals,

The baseband signal is supplied to the C / N
A detection signal corresponding to the value is output, and the AGC voltage is supplied, and when the AGC voltage becomes equal to or lower than the AGC voltage at which the gain control operation of the AGC circuit does not work, the detection signal having a predetermined value is output. / N value detection circuit,

A satellite broadcast provided with a control circuit which is supplied with the detection signal and outputs a control signal for controlling the polarization plane of a polarizer in the converter to the converter according to the detection signal. A receiver is provided.

[0020]

FIG. 1 shows a CS tuner which is an embodiment of the present invention.
Shown in. The same parts as those in the conventional example are designated by the same reference numerals, and a detailed description of those parts will be omitted.

This embodiment is provided with a C / N value detection circuit (10), and when the CS radio wave received by the CS converter (13) is a normal electric field, a detection signal corresponding to the C / N of the received radio wave. The polarization plane of the polariser is controlled by means of, and in the case of a weak electric field, the polarization plane of the polariser is controlled by a detection signal of a certain constant value. As a result, stable polarization plane control is always realized.

In general, C / N means a relative ratio between the level of Carrir of a signal being received and the ambient noise level including an adjacent channel, and C / N is an FM demodulated baseband signal. Can be correlated with the S / N of. Therefore, when the AGC circuit (2) operates and the amplitude of the baseband signal is constant, if the noise level of the baseband signal is detected and the signal is converted into a DC voltage, C / N
A DC voltage (detection signal) correlated with can be obtained.
In this embodiment, this method obtains the detection signal corresponding to C / N.

In FIG. 1, the C / N value detection circuit (10) is
Noise detection circuit (6), detection circuit (7), DC conversion circuit (8),
It is composed of a voltage comparison circuit (9).

The out-of-band noise signal of the video and audio baseband signals, which is the output from the FM demodulation circuit (3) in the CS tuner, is detected by inputting it to the noise detection circuit (6) having a bandpass filter. To do. After detecting the noise detected by the noise detection circuit (6) by the detection circuit (7),
By inputting the output to the DC converter (8),
A DC voltage corresponding to the noise level (that is, a detection signal corresponding to C / N) is output.

When the CS radio wave received by the CS converter (13) is a normal electric field, a DC voltage corresponding to the noise level is converted to C
Supply from the / N value detection circuit (10) to the antenna control circuit (11). Antenna control circuit (11), depending on the DC voltage,
Make C / N MAX (ie C / N in this case
The output voltage (detection signal) of the N-value detection circuit (10) becomes MAX), and the polarizer in the CS converter (13) is controlled by a control signal. The control signal is supplied from the antenna control output terminal (12) to the CS converter (13). C
In the S converter (13), the polariser is rotated by a motor or the like in response to a control signal to adjust the selectivity of the plane of polarization.

On the other hand, C received by the CS converter (13)
S electric wave becomes weak electric field (C / N decreases), AGC circuit
If the gain control operation of (2) does not work properly, the above method cannot obtain a correct detection signal according to C / N and cannot control the polarization plane correctly. Therefore, the voltage comparison circuit (9)
By this, the situation where the gain control operation of the AGC circuit (2) does not work properly is detected, and a detection signal of a certain constant value is output.

The voltage comparison circuit (9) supplies the AGC voltage supplied from the AGC circuit (2) and the reference voltage Vcc1 (this reference voltage Vcc1 is the boundary AGC voltage at which the gain control operation of the AGC circuit (2) does not operate normally). And). Then, when the supplied AGC voltage becomes equal to or lower than the reference voltage Vcc1, it is determined that the gain control operation of the AGC circuit (2) does not work normally, and the operational amplifier in the voltage comparison circuit (9) determines that C / The output voltage of the N value detection circuit (10) is C /
It is fixed at a voltage corresponding to N = 0. Antenna control circuit (1
In 1), the polarization plane can be correctly controlled even in a weak electric field by the voltage corresponding to C / N = 0. FIG. 2 shows the output characteristics of the DC voltage (detection signal) of the C / N value detection circuit (10).

With the above operation, the present embodiment does not require the polarization plane adjustment by the user as in the conventional case, and the C / N of the received signal is
Is automatically detected and the polarization plane is automatically adjusted, the labor of the adjustment is saved, and the polarization plane can be constantly adjusted in any input electric field.

[0029]

As described above, in the satellite broadcast receiver according to the present invention, the polarization plane adjustment of the polarizer provided in the converter is always stable and automatic in any input electric field. Can be done. .

[Brief description of drawings]

FIG. 1 is a diagram showing an example.

FIG. 2 is a diagram showing output characteristics of a C / N value detection circuit according to an embodiment.

FIG. 3 is a diagram showing a frequency array in CS broadcasting.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Frequency conversion circuit 2 AGC circuit 3 FM demodulation circuit 4 Video signal processing circuit 5 Audio signal processing circuit 6 Noise detection circuit 7 Detection circuit 8 DC conversion circuit 9 Voltage comparison circuit 10 C / N value detection circuit 11 Antenna control circuit 12 Antenna control Output terminal 13 CS converter

Claims (1)

[Claims] 1. A CS-IF signal output by supplying a signal received by a satellite broadcasting antenna to a converter, selecting a plane of polarization by a polarizer in the converter, and then performing frequency conversion in the converter. , A frequency converter circuit for converting the CS-IF signal into an intermediate frequency band and an amplitude of an output signal of the frequency converter circuit are detected, and an AGC voltage corresponding to the amplitude is generated. An AGC circuit that controls a gain by the AGC voltage to make the output constant, an FM demodulation circuit that FM demodulates an output signal of the AGC circuit and converts it into a video and audio baseband signal; The AGC voltage is supplied and the detection signal corresponding to the C / N value is output, and the AGC voltage is supplied to the gain control operation of the AGC circuit. A C / N value detection circuit that outputs a detection signal of a predetermined value when the voltage becomes equal to or less than the disappearing AGC voltage, and the detection signal is supplied, and the polarization plane of the polarizer in the converter is changed according to the detection signal. A satellite broadcast receiver, comprising: a control circuit that outputs a control signal to be controlled to the converter.